1. Field of the Invention
The present invention relates to the field of displaying technology, and in particular to a BOA (Black Matrix On Array) and a manufacturing method thereof.
2. The Related Arts
Liquid crystal displays (LCDs) have a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and are thus of wide applications, such as mobile phones, personal digital assistants (PDAs), digital cameras, computer monitors, and notebook computer screens.
Most of the liquid crystal displays that are currently available in the market are backlighting liquid crystal displays, which comprise a backlight module and a liquid crystal panel mounted to the backlight module.
In a thin-film transistor liquid crystal display (TFT-LCD), it is often to provide a layer of black matrix (BM) on a substrate to separate adjacent color resists, shield gaps between colors, and prevent light leakage or color mixture. The technique that forms the black matrix on a TFT array substrate is referred to as BOA. BOA can be used to overcome problems caused by mismatch of light shield zones due to positional shift of upper and lower substrates. This is particularly useful in curved display devices.
As shown in FIG. 1, in a manufacturing process of a conventional BOA liquid crystal panel, a layer of black matrix 120 is directly formed on an array substrate 100. This increases the film thickness h1 of the BM area of the array substrate 100. FIG. 2 shows a non-BOA structure (which is a black matrix on color filter (BM on CF) structure), meaning the black matrix 120 is formed on a CF substrate 200. It can be seen that the film thickness h1 of the BOA liquid crystal panel shown in FIG. 1 is greater than the film thickness h2 of the non-BOA liquid crystal panel shown in FIG. 2. Thus, for the BOA liquid crystal panel, since the site where black matrix is formed on the TFT substrate has an increased film thickness, a film thickness difference between the BM area and the non-BM area is made larger and a draft angle of the film between the BM and non-BM areas becomes steeper. In the subsequent metal process, a potential risk of line breaking due to an excessively large draft angle may occur, leading to defects. If an additional planarization layer is included, then additional operations may be needed, leading to other problems.